All about Project Baseline.

Project Baseline empowers passionate citizens to observe and record change within the world's aquatic environments in a way that fosters public awareness and supports political action.

Project Baseline Rheinauer See is one of many project around the world. The project monitors visibility, fish count, water temperature and quality at the Rheinauer See Mannheim, Germany. For this, we regularly go diving in the lake to measure, document and analyze fixed underwater stations. With this we establish a baseline to monitor and analyze changes over years.

Did you go diving at Rheinauer See and took a visibility and temperature measurment? It is now very easy to submit data for the project. Check out the data submission links for our existing project and for other places (ad-hoc).


Rheinauer See is a lake between the two cities of Mannheim and Heidelberg in the southwest of Germany. It is shared by water skiers, swimmers, fishermen and divers. Most of the area is surrounded by trees, reed and other vegetation. The area is accessible for pedestrians, visitors, divers and swimmers.

The lake faced many issues before 1999, until the number of divers was regulated. This was a bad development for the lake and now diving is restricted to the summer months (April til 15th December) and 10 divers per hour during daytime only. Since then the water quality got better. We are interested in the current state of the lake and want to monitor whether and how it will change in the future.

Underwater the lake has a few plants and the growth is dependent on the season of year. Weather and temperatures are influencing the visibility. By measuring data underwater in a reproduceable way, we want to get a better overview about how the lake changes between the seasons and over years. We hope to see patterns by documenting and analyzing the dive site. The lake has a good stock of fish and a maximum depth of 25 meters.

The lake is very close to the home of many of us. It is close to two larger cities and therefore we are diving there on a regular basis. Many other lakes are in the area, most of them being former gravel mining places like the Rheinauer See. But none of them is so close and convenient to go to. This is our diving backyard.


Rheinauer See is a small lake close to the city of Mannheim in the middle of a residential area. Being very close to the two larger cities of Heidelberg and Mannheim, the lake is a dive site for many divers after work or on weekends. Other activities take place as well, like fishing, swimming or relaxing on the shore. There is even a waterski plant in the western part of the lake.

The lake has a maximum depth of 25 meters, has an overall size of 0.12 square kilometers and is located 80 meters above sea level. It was originally used for gravel mining and was changed into a local recreational area. Underwater you can see different fish, a truck tire, underwater trees. In addition, there are two steep walls.

The number of divers is limited to 10 divers at the same time and diving is only allowed during daytime. Furthermore, diving is strictly prohibited between 15th December and 15th April.


The station is at around 11 meters. It is an old sunken fishing boat. The width of the boat is approximately 1.5 meters and it is around 6 meters long. At the station there is already a Secchi Disk attached, which we can use for visibility measurement. The boat has a clear shape, even in bad visibility and is easy enough for a diver to find to do a measurement.

The dive club managing the dive site has published a map of the lake.

GPS coordinates:

  • N 49° 24' 52.0''
  • E 008° 32' 11.3''
Latitude and Longitude:
  • 49.414440, 8.536474